Table Of ContentAustralian Entomologist, 2003, 30 (4): 181-183 181
THE IMMATURE STAGES AND SEASONALITY OF PETRELAEA
TOMBUGENSIS (ROBER) (LEPIDOPTERA: LYCAENIDAE)
P.R. SAMSON! and T.A. LAMBKIN?
'BSES Limited, PMB 57, Mackay Mail Centre, Qld 4741
"Queensland Department of Primary Industries, 80 Meiers Road, Indooroopilly, Qld 4068
Abstract
The immature stages of Petrelaea tombugensis (Rober), from Wongaling Beach in northern
Queensland, are described and illustrated. The food plant was Terminalia catappa L.
(Combretaceae). In Torres Strait, adults can be common just prior to the monsoon, coincident
with the first flush of Terminalia flowers.
Introduction
Petrelaea tombugensis (Rober) occurs within Australia in tropical areas of the
Northern Territory and Queensland (Braby 2000). Adults fly around
flowering Terminalia catappa L. and T. muelleri Benth. (Combretaceae) on
islands in Torres Strait and were observed ovipositing on T. catappa blossom
at El Arish in northern Queensland (Muller et al. 1998). Here we describe the
immature stages from material collected at Wongaling Beach near El Arish
and record observations on the flight period in Torres Strait.
Immature stages
Egg (Fig. 1). A flattened sphere; white; diameter 0.5 mm; sides and outer top
surface with ridges radiating from large knobs and forming mostly three-sided
pits; central part of top surface with irregular network of ridges.
First instar larva (Fig. 2). Buff coloured; head dark grey. With both short and
long colourless lateral hairs and colourless posterior hairs; prothorax (T1)
with two pairs of long brown dorsal and dorsolateral hairs directed forward
and colourless anterior hairs; T2 with two pairs of long brown dorsal and
subdorsal hairs directed forward and one pair of long brown dorsal hairs
directed backward; T3-abdominal segment 8 (A8) each with one pair of long
brown dorsal hairs; T2-A6 also each with one pair of short colourless dorsal
hairs.
Final instar larva (Figs 3-4). Green; T1 reddish brown anteriorly; A1 reddish
brown subdorsally; a reddish brown middorsal line most pronounced
posterior to dorsal points on A2-A6; head brown. Newcomer's organ and
tentacular organs present. Body with colourless anterior and posterior hairs
and dense stellate colourless or reddish brown secondary setae; T1 with ridge
in front of prothoracic plate bearing numerous pairs of colourless hairs; deep
dorsal divisions between segments T3-A7; T2-Al each with a pair of
subdorsal knobs and A2-A6 with middorsal pointed knobs; transverse ridges
on A7-A8; T2-A8 with lateral lobes, angular on A1-A6 but otherwise
rounded, each with one or two pairs of colourless hairs; T2-T3 each with two
pairs of colourless dorsal and dorsolateral hairs.
182 Australian Entomologist, 2003, 30 (4)
Figs 1-6. Petrelaea tombugensis; all except (3) from Wongaling Beach: (1) egg;
(2) first instar larva, head to right; (3) late instar larva from Thursday Island, Torres
Strait; (4) final instar larva feeding; (5) pupa; (6) Terminalia flower eaten out by
larva. Scale bars (1-2) = 0.5 mm, (3-6) = 2 mm.
Australian Entomologist, 2003, 30 (4) 183
Pupa (Fig. 5). Covered with short colourless hairs; thorax and wing covers
greyish brown and abdomen yellowish brown, sparsely covered with dark
brown spots; a dark brown middorsal patch on T1; dark brown patches
laterally on T2 and dorsolaterally on T3; abdomen with dark brown
dorsolateral patches, especially on Al and A5-A6, and with a brown
middorsal line; attached by anal hooks and central girdle.
Life history notes
At Wongaling Beach, eggs of P. tombugensis were found in December 2001,
laid singly on flower buds of Terminalia catappa. The feeding habits of early
instar larvae were not closely observed, but larvae ultimately died when
supplied only with unopened buds. Larger larvae fed only on open flowers
while buds on the same spikes were not eaten. Larvae curled across the tops
of the flowers and ate the nectaries, leaving the stamens and calyx intact (Figs
4, 6). The apparent dependence on open flowers may explain the larval
mortality also recorded by Muller ef al. (1998) when they attempted to rear
this species on Terminalia flower buds. The larval and pupal stages occupied
about 2 weeks and 1 week respectively, when reared in southern Queensland
at ambient conditions in January. Adults of this species have recently (April
2002) been collected flying around 7. catappa at Townsville by Graham
Wurtz (S. Johnson, pers. comm.), extending the known range substantially
southwards from El Arish.
Adult seasonality
Muller et al. (1998) briefly outlined information on adult habits and flight
period in the wet tropics of northern Queensland and in Torres Strait. Since
then, one of the authors (TAL) has recorded more details of the seasonality of
this species in Torres Strait. Adults are abundant just prior to the monsoon,
coinciding with the first flush of flowers on leafless trees of T. catappa and T.
muelleri (both species tend to flower simultaneously). Large numbers of
adults (7100) have been observed flying around mature trees of T. catappa on
Murray Island in late October and 7. muelleri on Sue Island in late December.
P. tombugensis is generally less common over the remainder of the flowering
period, which can last until May, just prior to the dry season, after which both
Terminalia species become almost leafless. The recorded flight period is
September-May (Muller et al. 1998).
References
BRABY, M.F. 2000. Butterflies of Australia: their identification, biology and distribution.
CSIRO Publishing, Melbourne; xxvii + 976 pp.
MULLER, C.J., OLIVE, J. and LAMBKIN, T.A. 1998. New records for Petrelaea tombugensis
(Rober) (Lepidoptera: Lycaenidae) in Queensland. Australian Entomologist 25: 61-63.
